The orthography of a language specifies a standardized way of using a specific writing system (script) to write the language. Where more than one writing system is used for a language, for example Kurdish, Uyghur, Serbian or Inuktitut,Turkish, there can be more than one orthography. Orthography is distinct from typography.

Most natural languages developed as oral languages, and writing systems have usually been crafted or adapted afterwards as representations of the spoken language. In an etic sense, the rules for writing systems are arbitrary, which is to say that any set of rules could be considered "correct" if the users of the language mutually agreed to convene upon that set of rules as the standard way to represent the spoken language. However, as standardization takes stronger hold, an emic epistemology of "right and wrong" develops, in which compliance with, or violations of, the standards are viewed as right, or wrong, in a way analogous to moral right and wrong, and in which each word has a written identity that is no less standardized than its oral-aural identity, which is emically unitary. The term orthography is sometimes used in a linguistic sense to refer to any method of writing a language, without judgment as to right and wrong, with a scientific understanding that orthographic standardization exists on a spectrum of strength of convention. But the original sense of the word stem, which evolved long before linguistic science, implies a dichotomy of correct and incorrect, and the word stem is still most often used to refer not just to a way of writing a language but more specifically to the thoroughly standardized (emically "correct") way of writing it.

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An orthography may be described as "efficient" if it has one grapheme per phoneme (distinctive speech sound) and vice versa. An orthography may also have varying degrees of efficiency for reading or writing.[citation needed] For example, diverse letter, digraph, and diacritic shapes contribute to diverse word shapes, which aid fluent reading, while heavy use of apostrophes or diacritics[citation needed] makes writing slow, and the use of symbols not found on standard keyboards makes computer or cell phone input awkward.

A phonemic orthography is an orthography that has a dedicated symbol or sequence of symbols for each phoneme (distinctive speech sound) and vice versa, that is, graphemes and phonemes are bijective functions of one another. Russian, Spanish and Italian are close to being phonemic, and English is among the least phonemic.

A morpho-phonemic orthography considers not only what is phonemic, as above, but also the underlying structure of the words. For example, in English, /s/ and /z/ are distinct phonemes, so in a phonemic orthography the plurals of cat and dog would be cats and dogz. However, English orthography recognizes that the /s/ sound in cats and the /z/ sound in dogs are the same element (archiphoneme), automatically pronounced differently depending on its environment, and therefore writes them the same despite their differing pronunciation.

Korean hangul has changed over the centuries from a highly phonemic to a largely morpho-phonemic orthography, and there are moves in Turkey to make that script more morpho-phonemic as well. Japanese kana are almost completely phonemic, but has a few morpho-phonemic aspects, notably in the use of ぢ di and づ du (rather than じ ji and ず zu, which is how they are pronounced) when the character is a voicing of an underlying ち or つ – see rendaku.

A "deep" orthography is one in which there is not a one-to-one correspondence between the letters and the phonemes in the language, such as that of English. Most languages of western Europe (which are written with the Latin alphabet), as well as the modern Greek language to a lesser extent (written with the Greek alphabet), have deep orthographies. In some of these, there are sounds with more than one possible spelling, usually for etymological or morpho-phonemic reasons (like /dʒ/ in English, which can be written with ⟨j⟩, ⟨g⟩, ⟨dg⟩, ⟨dge⟩, or ⟨ge⟩). In other cases, there are not enough letters in the alphabet to represent all phonemes. The remaining ones must then be represented by using such devices as diacritics, digraphs that reuse letters with different values (like ⟨th⟩ in English, whose sound value is normally not /t/ + /h/), or simply inferred from the context (for example the short vowels in abjads like the Arabic and Hebrew alphabets, which are normally left unwritten). The syllabary systems of Japanese (hiragana and katakana) are examples of almost perfectly shallow orthography – exceptions include the use ぢ and づ (discussed above) and the use of は, を, and へ to represent the sounds わ, お, and え, as relics of historical kana usage.

Another term to describe this characteristic is "defective orthography". This term, however, clearly implies the superiority of shallow orthographies—a point that advocates of morphophonemic writing would dispute. Using the terms "deep" and "shallow" is therefore more neutral in relation to the question of what types of orthography are superior.

Complex orthographies often combine different types of scripts and/or utilize many different complex punctuation rules. Some widely accepted examples of languages with complex orthographies include Thai, Chinese, Japanese, and Khmer.[citation needed]